Fix Duplicate execution of workflows

[Salkinnoma]

Fixes Issue #8955
Validate Gradle Wrapper and validate-workflows are now executed only on PR

[wmontwe]

LGTM

[kewisch]

@wmontwe do we only need to do this on pull requests, or would it be helpful to do it on pushes to the main branch as well? The original issue was that the task is run twice on pull requests because a PR is also a push but to the PR branch.

[Salkinnoma]

So there is no Branch protection to prevent pushes directly to main?

[kewisch]

There is, I guess we'd be safe on main since everything needs a pull request, good point. We have beta and release branches where we do uplifts from main and could theoretically push directly, which might need to happen if we have to change a patch due to merge conflicts. Am I being overcautious here?

[wmontwe]

@kewisch There are no pushes allowed to main, all changes have to be done by a pull-request.

Push was allowed a while ago, but following best practises this had been disabled. Just the workflows haven't been changed accordingly.

Exceptions are beta and release branches where normal pushes are allowed, but force pushes are disabled. This could be changed where the uplifts are required to have a branch and code review as well. This would be recommended, especially when an uplift needs further changes to be applied to beta or release.

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